Remove unused Propa example

The `Propa.myc` example was not being used and has been removed to clean
up the examples directory.

examples/data_stream_print.myc

@@ -8,7 +8,6 @@
   (def cnt 1)
   (def gs (series 2))
 
-;IDEE (pipe lookback [EURUSD acc] --> series acc
   (pipe [EURUSD GER40]
     (fn [eu ge]
       (do
@@ -20,4 +19,19 @@
       )
     )
   )
+
+  ; TODO: IDEE - pipe mit automatischer Value-Akkumulation: pipe <lookback> <inputs>
+
+  (pipe 2 [EURUSD GER40]
+    (fn [eu ge]
+      (do
+        ; eu und ge werden hier zu Serien mit lookback 2
+        (def dax (.close (ge 0)))
+        (push gs dax)
+        (def eur (- dax (ge 1)))
+        (print cnt ": dax=" eur " (" (/ eur (.close (eu 0))) "$)" )
+        (assign cnt (+ cnt 1))
+      )
+    )
+  )
 )